High impact LLDPE films

Abstract

Blown films of linear low density polyethylene are produced by a high stalk process comprising extruding the linear low density polyethylene through an annular die to form an extruded tube of molten material, cooling the extruded tube while drawing the tube so cooled, to maintain the tube diameter identical to that of the annular die and expanding the tube or bubble to attenuate the walls thereof by introducing a gas to the interior of the tube or bubble. The resulting films are characterized by superior impact strength and MD tear resistance.

What is claimed is:  
     
       1. A blown film comprising a copolymer of ethylene and an alpha olefin of 3 to 10 carbon atoms having a density of 0.910 to 0.940 g/cc, and having a dart drop impact value, wherein said blown film is in the form of a high stalk extrudate of said copolymer which high stalk extrudate form results in an increase of said dart drop impact value by at least 25%; 
       wherein the copolymer exhibits a Mz/Mw value of 4 to 10;  
       wherein the copolymer was formed in the presence of dimethylaluminum chloride as a cocatalyst; and  
       wherein said high stalk extrudate exhibits a haze of greater than 15 (as determined by ASTM D-1003); and a gloss of less than 50 (as determined by ASTM D-2457).  
     
     
       2. The film of  claim 1 , wherein the alpha olefin is 1-butene, 1-hexene or 1-octene. 
     
     
       3. The film of  claim 1 , wherein the alpha olefin is 1-hexene. 
     
     
       4. The film of  claim 1 , wherein the dart impact value is in the range of 50 to 800 g. 
     
     
       5. The film of  claim 1 , formed by a process comprising extruding said copolymer to form a tube and cooling the tube with one air ring. 
     
     
       6. The film of  claim 1 , wherein the dart drop impact value is in the range of 70 to 1000 g. 
     
     
       7. The film of  claim 1 , wherein the dart drop impact value is in the range of 200 to 800 g. 
     
     
       8. The film of  claim 1 , wherein the dart drop impact value is in the range of 350 to 800 g. 
     
     
       9. The film of  claim 1 , wherein said film has an MD tear resistance in the range of 200 to 500 g/mil. 
     
     
       10. The film of  claim 1 , wherein said film has an MD tear resistance in the range of 250 to 500 g/mil. 
     
     
       11. A film comprising a copolymer of ethylene and an alpha olefin of 3 to 10 carbon atoms having a density of 0.910 to 0.940 g/cc and a melt flow ratio of 25 to 45; 
       wherein the copolymer has an Mz/Mw value of at least 3.5;  
       wherein the copolymer is formed in the presence of dimethylaluminum chloride as a cocatalyst; and  
       said film having a dart drop impact value (as determined by F50, ASTM D-1709) of 50 to 1000 g and MD tear resistance (as determined by ASTM D-1922) of 50 to 500 g/mil.  
     
     
       12. The film of  claim 11 , wherein the Mz/Mw value is from 4 to 10. 
     
     
       13. The film of  claim 11 , wherein the dart drop impact value is in the range of 50 to 800 g. 
     
     
       14. The film of  claim 11 , wherein the dart drop impact value is in the range of 70 to 1000 g. 
     
     
       15. The film of  claim 11 , wherein the dart drop impact value is in the range of 200 to 800 g. 
     
     
       16. The film of  claim 11 , wherein the dart drop impact value is in the range of 350 to 800 g. 
     
     
       17. The film of  claim 11  wherein the MD tear resistance is in the range of 200 to 500 g/mil. 
     
     
       18. The film of  claim 11 , wherein the MD tear resistance is in the range of 250 to 500 g/mil. 
     
     
       19. The film of  claim 11 , wherein said film is formed by a high stalk extrusion process. 
     
     
       20. The film of  claim 11 , wherein said film has a haze greater than 15 (as determined by ASTM D-1003) and a gloss less than 50 (as determined by ASTM D-2457).